1. Field of the Invention
The present invention relates to a force and deflection sensor. In particular, the invention relates to an flexible shell formed with an elastomer having passageways formed by apertures in the shell, with an optical fiber having one or more Bragg gratings positioned in the passageways for the measurement of force and deflection.
2. Description of the Related Art
Future robots are expected to free human operators from difficult and dangerous tasks requiring high dexterity in various environments. One example is an extra-vehicular repair of a manned spacecraft that would otherwise require hazardous work by human astronauts. Another example is robotic surgery in which accurate manipulation is crucial. Operating complicated tools and performing delicate tasks require a manipulator of great precision and coordination. Therefore, force sensing is one of the most critical requirements for this type of robot control. Typically, robots have a modest number of mechanical sensors, often associated with actuators or concentrated in a special device such as a force sensing wrist. As a result, robots often poorly identify and respond to unexpected and arbitrarily-located impacts.
One object of the invention is a light-weight, rugged appendages for a robot that features embedded sensors so that the robot can be more aware of both anticipated and unanticipated loads in real time. A particular class of optical sensors, Fiber Bragg Grating (FBG) sensors, is promising for space robotics and other applications where high sensitivity, multiplexing capability, immunity to electromagnetic noise, small size and resistance to harsh environments are particularly desirable. In addition, the biosafe and inert nature of optical fibers making them attractive for medical robotics. FBGs reflect light with a peak wavelength that shifts in proportion to the strain to which they are subjected. This wavelength shift provides the basis for strain sensing with typical values for the sensitivity to an axial strain being approximately 1.2 pm/microstrain at 1550 nm center wavelength. In combination with a prior art FBG interrogator, submicrostrain resolution measurements are possible. In addition, the strain response is linear with no indication of hysteresis at temperatures as high as 370° C. and, with appropriate processing, to over 650° C. Multiple FBG sensors can be placed along a single fiber and optically multiplexed. FBG sensors have previously been surface attached to or embedded in metal parts and composites to monitor stresses.